The Hardy-Weinberg Principle and Allele Frequencies · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

When gene pools stand still

Science · Genetics & Evolution · ages 17-18
Name ______________________   Date ____________

  1. Which of these does the model assume?

    • Populations stay tiny and isolated
    • Mating is random across the population
    • Selection favours one allele strongly

  2. Which pair of equations runs the Hardy-Weinberg model?

    • p plus q equals 1 with p squared plus 2pq plus q squared equals 1
    • p times q equals 1 with p squared minus q squared equals 1
    • p minus q equals 1 with 2p plus 2q equals 1

  3. A population in Hardy-Weinberg equilibrium keeps the same allele frequencies across generations.

    Circle one:   True   False

  4. How do you tally alleles from genotype counts?

    • Count every individual exactly once regardless of type
    • Count only the heterozygotes and ignore the rest
    • Count each homozygote twice and each heterozygote once

  5. In 100 plants there are 30 AA, 40 Aa and 30 aa. What is the frequency of allele A?

    Answer: ______________

  6. A small inbred group mates among relatives. Which assumptions break?

    • Huge population size and random mating
    • No mutation and no gene flow
    • The equations themselves stop adding up

  7. Allele frequencies shift steadily across generations. What does that show?

    • The population sits in perfect equilibrium
    • The counting method must be at fault
    • A force such as selection is pushing the gene pool

  8. In 100 people, 4 are affected by a recessive condition. What is the carrier frequency?

    Answer: ______________

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Answer key

For grown-ups. Fold this page away before handing over the rest.

When gene pools stand still W1-mt_eJjwZ2qVAE-s1

  1. Mating is random across the population · Random mating, huge size, and no selection are all on the assumptions list.
  2. p plus q equals 1 with p squared plus 2pq plus q squared equals 1 · Allele frequencies sum to one, and the genotype mix follows from squaring that sum.
  3. True · Still frequencies are the definition of equilibrium and of no evolution there.
  4. Count each homozygote twice and each heterozygote once · Homozygotes carry two copies of the allele and heterozygotes carry one.
  5. 0.5 · A copies are 60 plus 40, which is 100 of 200 alleles, so p is 0.5.
  6. Huge population size and random mating · Small groups drift by luck and relatives pair non randomly, breaking two assumptions at once.
  7. A force such as selection is pushing the gene pool · Equilibrium means stillness, so a lasting shift is evidence of evolution.
  8. 0.32 · q squared is 0.04, so q is 0.2, and 2 times 0.8 times 0.2 is 0.32.
Worksheet · LightMySky